There have been a decent amount of studies done to look into this and the results have been largely the same: preschool does lead to gains, but they're primarily short-term and rarely sustained. While members of some studies did go onto benefit from significant gains such as higher income and lower incarceration rates, the underlying issue of disproportionate racial enrollment in preschool remained. Preschool reform does need to happen, but it won't be the thing to fix the achievement gap.
This idea aims to fix the achievement gap when it starts to noticeable manifest in students, rather than root out the problem. Student-based reforms aim to cultivate a heightened interest and appreciation in academics and academic-adjacent activities. The No Child Left Behind Act in 2001 followed this logic and has been encouraging student achievement for almost two decades. Standards-based grading has been used to reinforce this in the past, too. However, none of these have shown advantages. For as long as they've been in place, gains should have been made by now.
This category can be broken into two subparts, the first being overall reform. This overall reform aims to better equip all teachers to help encourage and support disadvantaged students, as well as provide them with the necessary resources. At the moment, education is severely underfunded nationwide, so whether or not this is feasible is up in the air. The second part is giving students teachers that look like them. A study found that black students who have black teachers tend to "achieve" more and perform better on assessments (Porter, 2020). This solution, however, is controversial and can easily turn into a problem in and of itself. There are no studies done that show what sort of social or emotional effects this might have on students and this could easily fall prey to segregation efforts. There isn't enough research done about this and too many accompanying pitfalls for this to be a good option to pursue.
Like many issues, there is no easy fix or straight path forward. Studies are contradictory or inconclusive, some solutions are impossible to fund or just simply not feasible, and, of course, there's the matter of actually getting things passed through Congress. Most, however, can agree that the achievement gap starts to form before students even step foot into a school, which makes it all the harder to address.